Credit

Caption

Banded rock. Ancient ironstone strata, some two billion years old, is seen here as regular layers of hard rock of almost equal width alternating with iron-laden red and darker rock. This ancient rock was laid down in every continent due to the availability of oxygen produced by the first photosynthetic organisms such as cyanobacteria. More than 90% of the Earth's mineable iron was deposited between 2500 and 1800 million years ago. This type of rock is variously decribed as haematite-quartzite, banded iron formation, banded jasper or calico rock. Photographed at Fortescue Falls in Hamersley Range National Park, Central Pilbara, in the north-west of Western Australia.